In many environments, particularly xerographic reproduction machines, it may be desirable to provide a sheet feeder wherein the sheets are removed from the bottom of a stack. Bottom feeders are particularly useful for feeding blank sheets of copy paper into a copy machine to enable continual replenishment of the stack without stopping operation of the machine as is necessary with top sheet feed devices. Further, if the sheet feeding device is to be utilized for feeding documents to the platen of a copy machine for imaging thereat, it may be desirable to feed from the bottom of the stack to maintain the proper pagination so that the output from the copy machine is pre-collated. In certain modes of operation, it may also be desirable to insert the copied document into the bottom of a stack of documents already copied so that the proper page orientation is maintained to enable subsequent copying in the proper order.
In a xerographic type reproduction machine, the developer material in the more common machines is permanently affixed to the copy sheet by the heat and pressure. Thus, sheets discharged from the xerographic machine may be quite warm and may cool into a non-planar condition. Therefore, in many instances, it may be desirable to provide a copy output tray wherein the sheets are inserted into the bottom of the stack to maintain the sheets in a planar condition as they are cooled.
Another problem that may be encountered in paper feeders is that in attempting to feed sheets seriatim, the feed mechanism is ordinarily energized and de-energized for each sheet being fed to provide the proper spacing therebetween. This results in fairly high inertial loads to start and stop the feed mechanism between each feed operation.
It is therefore the object of the present invention to provide a universal feeder-stacker adapted to remove sheets seriatim from the bottom of a stack of sheets or to insert sheets seriatim into the bottom of a stack of sheets and provide feed means associated therewith adapted for constant motion while providing intermittent feeding of sheets with minimal forces exerted on the sheets being handled thereby.